Finding the right clock key
Here we have clock keys in all the sizes available. We get many calls asking what key their clock takes and over the phone it is difficult to say what key size is needed. Read More »
Best to read the below text on how to use the clock keys chart and get the correct sized key to wind your clock. What can be said is most larger German movements take a number 8 key.
So if your clock movement is made in Germany, is 5 x 5 square or 6 x 9, it will take a number 8 usually. If the clock movement is made in Germany and it's round, it's usually number 4.
If you have a 31 day clock, or a Korean clock, or a commonly produced early American time strike movement, then it's usually number 7. However, if you want to be sure with all this then use the below chart.
Double End Clock Key (F / S at 12) Note
If you see an F / S or an A / R around the 12 o’clock area of the clock dial, this is called a regulator. So for F / S this means fast or slow, and the A / R would represent advance or retard. Read More »
So turning the arbor toward F will make the clocks time run faster and the opposite direction for slow. To turn this you would use the small end of your clock key. If the key has been lost at one point then someone could have replaced the key with a single end key instead of double. The double end key is what you would need instead, one for the winding up the clock and the other side for the F / S regulation. There are many sizes and combinations for the double end key and it may be tricky to get the right size. So you may just want to get the 4 pack of double end keys we offer. This is the top 4 most common double end clock keys that are used so the odds are with you that you will get the correct key with both sides fitting your clock movement.
If the pendulum leader is too short then you may need to adjust the fast / slow beyond what the regulator is designed to adjust. If this is the situation you may just want to get an adjustable bob to regulate the clock instead. If you get the adjustable bob instead you do not need a double end key. You only need to adjust the nut on the bottom of the pendulum bob as to raise the bob to speed up the clock time or the opposite to slow the clocks time down. So if you choose to get the adjustable bob, please see it displayed at the following link. The adjustable pendulum bob comes in three sizes, or bob diameters. Usually the middle sized bob or the smaller bob is fine for most clocks.
Using the clock key chart
To get the key you need, measure the shaft the key is to go on to, then use this chart to get the key size # you need. Please do not call asking what key your clock needs, as you will be told it would still have to be measured. Again, you are measuring the shaft that the key goes onto in MM and then using the below chart.
Almost all post 1960 mechanical clocks, made in Germany take a size #8 key or crank, unless the movement is round. The round ones take a number 4 usually.
Clock key sizing chart
Shaft width / Key #
- 1.75mm = 000 Key
- 2.0mm = 00 Key
- 2.25mm = 0 Key
- 2.5mm = 1 Key
- 2.75mm = 2 Key
- 3.0mm = 3 Key
- 3.25mm = 4 Key
- 3.5mm = 5 Key
- 3.75mm = 6 Key
Shaft width / Key #
- 4.0mm = 7 Key
- 4.25mm = 8 Key
- 4.5mm = 9 Key
- 4.75mm = 10 Key
- 5.00mm = 11 Key
- 5.25mm = 12 Key
- 5.5mm = 13 Key
- 5.75mm = 14 Key
- 6.0mm = 15 Key
Brass Single End Clock Key
Available in many sizes, this is the most popular choice on this page.
5 Prong Clock Key Set
These two 5 prong clock keys will fit just about every clock winding arbor.
Item #CK8 -- $19
Available in 0 to 13. This crank is usually used for the OGee mantle clock.
Four most popular double end clock keys. There is always much confusion for people to get the proper double end key, so we offer this set of 4 keys most frequently used. These have the Small end for regulating some clocks as well as the end to wind.
Item #CK2-- $19
12 Assorted keys and setters for alarm clocks such as big ben, baby ben, and others.
Item #CK5-- $9
Useful tool to determine the size of your clock keys when it is not indicated on the keys themselves.
Item #CK13-- $19